Edward B. Rastetter, Ruth Yanai, R. Quinn Thomas,

Matt Vadeboncoeur, Tim Fahey, Melany Fisk,

Bonnie Kwiatkowski, and Steven Hamburg

Hubbard Brook Annual Meeting

July 2014

Recovery from disturbance requires

resynchronization of ecosystem

nutrient cycles

Ecological Applications 23: 621-642. 2013

CH2O

N

P

Plants

Soil

Organic

Matter

Soil

Solution

High dependence on internally recycled N & P Highly synchronized cycles

Low external

nutrient supply

Response to disturbance depends upon a

redistribution of nutrients already in the ecosystem

The Multiple Element Limitation (MEL) Model

Plants

Coarse

Woody

Debris

Phase I

SOM

Phase II

SOM

PO4

2o

Mineral

P

1o

Mineral

P

NH4

DON

NO3

PS RA

RH1

RH2

LNH4

LDON

LNO3

LPO4

INO3

INH4

IDON

IPO4

DNO3

C

NP

Snow

Pack

Soil

Water

Ppt

RO

ET

EI

H2O

Biomass Recovery for Northern Hardwood Forests

Steve Hamburg’s

data

0

5

10

15

20

25

0 50 100 150 200 250

Bole only harvest

Series8

Series9

Constant turnover

Series3

Ab

oveg

rou

nd

bio

mass (

kg

DW

/m2)

Forest age (years)

Forest age (years)

Lit

ter

fall

(kg

DW

/m2/y

r)0

0.2

0.4

0.6

0 50 100 150 200

Calibration to

Tim Fahey’s data

Biomass recovery is fueled

predominantly by nutrients

derived from sources within

the ecosystem.

During early succession,

Phase II SOM serves as a

"capacitor" storing nutrients

that are used later in recovery.

During mid to late succession,

the nutrients come from older

phase II SOM.

During early succession,

those nutrients come from the

coarse and fine slash left as

coarse woody debris and

phase I soil organic matter

(SOM).

0

2

4

6

8

10

12

14

0

2

4

6

8

10

12

14

0 50 100 150 200

Peak season biomass

Coarse woody debris

Phase I SOM

Phase II SOM

40

42

44

46

48

50

52

54

0

2

4

6

8

10

12

14

0 50 100 150 200

600

630

660

690

720

750

780

0

30

60

90

120

150

180

0 50 100 150 200

kg

C / m

2g

N / m

2g

P /

m2

kg

C / m

2g

N / m

2g

P /

m2

Bio

mass,

Co

ars

e W

oo

dy D

eb

ris,

an

d P

hase I S

OM

Ph

ase I

I S

OM

Forest age (years)

SS

Recovery from a bole-only harvest

Total-ecosystem element budget

following a bole-only harvest

The N loss is necessary to resynchronize the late-succession N and P cycles

as woody tissues accumulate in the biomass.

About 10% of the C and 1% of the N & P are removed at harvest.

Most of the C, N, & P losses are during the post-harvest recovery,

first of C & P and much later by N.

The C is easily recovered from a readily available outside source, N & P are not.

The P loss is necessary to resynchronize the early-succession N and P cycles

to the low-biomass conditions.

60

70

80

90

100

0 50 100 150 200

Total CTotal NTotal P

% o

f s

tea

dy s

tate

YearSS

Carbon (g C m-2)Mature

stand

Bole-only

harvest

Whole-tree

harvest

Post

hurricane

Plants 12006 120.06 120.06 120.06

Coarse Woody Debris 1313 10029.8 3450.5 12279.8

Phase I SOM 2970 3889.14 3493.44 3889.14

Phase II SOM 12770 12770 12770 12770

Removed in harvest 0 2250 9225 0

Total 29059 29059 29059 29059

0

2

4

6

8

10

12

14

0 50 100 150 200

Whole tree harvest

Bole only harvest

Hurricane blowdown

Effect of leaving different amounts of high-C slash (early succession)

Effect of removing different amounts of N & P (late succession)

Pla

nt

bio

mass (

kg

C/m

2)

Forest age (years)

SS

Less s

lash;

less im

mo

bili

za

tion

;

faste

r re

co

ve

ry Ca

no

py c

losu

re;

mo

re s

lash

;

mo

re im

mo

bili

za

tio

n;

slo

we

r re

co

ve

ry

More slash; more immobilization; slower recovery

High initial nutrient removal;

lower recovery

Low initial nutrient removal;

higher recovery

Nutrients not limiting; all trajectories the same

4) If those resources lost early in succession cannot be recovered quickly

enough, then the loss of the other resources might be necessary to

reestablish the synchronization among resource cycles late in succession.

3) Even disturbances that result in only small losses of resource capital can

disrupt the synchronization among resource cycles and thereby cause

the loss of some resources early in succession.

1) Many mineral resources are tightly cycled within ecosystems and have

only small exchanges with external sources and sinks. This tight

recycling means that the resource cycles have to be synchronized.

Conclusions

2) Because of changes in allometry and stoichiometry, the element cycles

synchronize to different relative cycling rates ad different times in

succession

CH2O

N

P

Plants

Soil

Organic

MatterSoil

Solution 0

2

4

6

8

10

12

14

0 50 100 150 200

Whole tree harvest

Bole only harvest

Hurricane blowdown

Pla

nt

bio

ma

ss

(k

g C

/m2)

Forest age (years)

Limitation on 200-year recovery largely determined by N:P of the

internal nutrient cycles

Limitation on long-term recovery largely determined by N:P of the

external nutrient supply